package task_hash;

use strict;
use warnings;
use Digest::MD5 qw(md5_hex);

my @keywords = qw(
	auto 	 break 	    case 	    char 	const 	    continue 	default 	do
	double 	 else 	    enum 	    extern 	float 	    for 	    goto 	    if
	int 	 long 	    register 	return 	short 	    signed 	    sizeof 	    static
	struct 	 switch 	typedef 	union 	unsigned 	void 	    volatile 	while

	printf scanf include stdio math stdlib malloc calloc realloc free

	bool catch class const_cast delete dynamic_cast explicit false friend
	inline mutable namespace new operator private protected public
	reinterpret_cast static_cast template this throw true try typeid typename
	using virtual wchar_t 
	
	cons car cdr atom null list defun lambda setq eval funcall apply format princ 
	if cond unless eq eql equal equalp let loop nil
	
	as case of class data default deriving do forall foreign hiding if then else import infix infixl infixr 
        instance let in mdo module newtype qualified type where	
);

# Usage: $hashref = hash($sourcecode);
sub hash($)
{
	my ($contents) = @_;
	my %keywords;
	map { $keywords{$_} = 1; } @keywords;
	my %result;

	$result{source} = md5_hex($contents);

	$contents =~ s/\/\*.*?\*\///gs; # I know that's not exactly correct
	$contents =~ s/\/\/.*//g;
	$contents =~ s/\b/ /g;
	$contents =~ s/(\W)(?=\W)/$1 /g;
	$contents =~ s/[\s\n\r]+/ /g;
	$result{compressed} = md5_hex($contents);

	my %dictionary;
	my $counter = 0;

	while ($contents =~ /\b([a-z]\w*)\b/gi)
	{
		next if defined $keywords{$1};
		$dictionary{$1} = sprintf "ID%05d", ++$counter;
	}

	foreach my $word (keys %dictionary)
	{
		$contents =~ s/\b$word\b/$dictionary{$word}/g;
	}

	$result{encoded} = md5_hex($contents);

	my @contents = split /\s+/, $contents;
	my $fingerprints = '';
	my @fplist;
	foreach my $token (@contents)
	{
		my $value = (defined $keywords{$token} ? 'k' : ($token =~ /^ID/ ? 'i' : 
								($token =~ /^\d+$/ ? 'n' : $token)));
		$fingerprints .= $value;
		push @fplist, $value;
	}

	$result{fingerprints} = $fingerprints;
	$result{fplist} = \@fplist;

	return \%result;
}

1;